Reaction of polycarboxylic acids and polythiols



Patented Aug. 7, 1951 -ATES PATENT OFFICE 2,568,133 EACTION F POLYCARBOXYLIC ACIDS AND POLYTHIOLS oseph 0. Patrick, Morrisvllle, Pa., and Harry B. erguson, Trenton, N. J., assignors to Thiokol orporation, Trenton, N. .L, a corporation of Pelaware 'No Drawing. Application November 7, 1944,

Serial No. 562,395 I 1 Claim. (Cl. 260-18.!)

2 It is evident that the foregoing compounds are composed of either carbon, hydrogen and sulfur. or carbon, hydrogen, sulfur and oxygen.

For copolymerization purposes the invention a I 5 employs the polyhydric alcohols in general, with the present invention various specific examples thereof being given in eneral are reacted with polythe following list: M at is, organic compounds conme n groups, d TABLEII pounds eing therefore polyfunctional in respect Glycols in general exemplifi y t f llowof said mercapto groups, are reacted with polyt basic acids to produce polymers, which-may be cmoncmomethelena w A 1 :Stelis. fiol'e ovel', 00- CH3 CHOH CH,OH, propylene glycol l are accm'dance 110cm. cmcmon, trimothylone glycol th mmnmon. obtained by reacting CH|.CHOH.CHOH.CKa,butsndiol 2,3

alohmw h polybasic acids Such copolymers CH:.CH0H.CH1.CH|0H,butandiol1,3 may also be obtained by first reacting the poly- M mercapto compounds with the polybasic acid, (Cmhcwm immtyie 7? andzseparatelygreacting a polyhydric alcohol with M m wmr mmmm 'giiipolybasiciacld' and then reacting the poly- H(CH:),.SS(C H:)1-0H fise'parately produced to obtain said where n may vary from 2 to 20 or more. copolymei iproducts. 01cm.cmcmsscmcmcmon Z' -Variousiexamples of the genus or class designated as polymercapto compounds and employed Ha H1 in accordance with the present invention are o cnQcmsacmOcm-on the following table.

polymers and niques.

TABLE I TABLE 111 a E Polyhydric alcohols containing three or more on 3 groups, in general exemplified by the followyvary from2to 20 or more. mg; CHa0H.CH0H.CH|0H,glycerine I cmcnomcnomcmon,bunntrloi1,2,3 I M 85 The erythritols, having the empirical formula HCHPCIFCHCHSH v 05 3a.cHon.cnon.cmon-o on,om., pontsorylll- H: A]; The penta and hexalwdric alcohols including:

sm. o fi' CH on H Xylitol Dulcitol EJ SHF Mannitol 5H 5H Polybasic acids in general may be used, e. g.. BBC on SE maleic, fumaric, succinic, malic, adipic, citric.

tartaric, phthalic, tricarballylic, ego, or the cor- Hscmocdisg responding anhydrides. It is evident that the foregoing acids are composed of carbon, hydrogen and oxygen.

The principles of the invention will be defined where 0 may vary from 2 to 20 or more.

he claims ill the H8.CH2.CECH:.SS.CH:.CH.CH:.SH gezmo example ustmted by following cmcncmcmsacmcmcmcm Example Q 1 Reaction between dimercapto ethane and maleic acid. The reaction is carried out between HS.C .0 .0.0 .o.cn.cn. HS g: gi z 8s (3H, 3: :35; 3: 1 mol of dimercapto ethane and 1 mol of maleic 1 famolofhydro- HS CH2 cm s cm cm SH acid As a catalyst, /1oo o chloric acid may be'used. The reaction is carried flfl-c zfizzout in an esteriflcation flask fitted with a trap ns-cm'clkcfl 015-53 go and reflux condenser so that the water formed asaresultofthecondensationmayberemoved. About200cc.ofbenxenemaybeaddedtoaidin the elimination of water. The mixture is then heated to the boiling point of benzene until the theoretical volume of water has collected in the trap,thebenseneisthendistiliedoifonawater bath andtheheatingonthewatcrbathmaybe continued from to 8 hours. The resultant product when collected is a wax-like substance somewhatresemblingparaiiinwaxinappearance. If thepolymerimtionhasbeenpushedtoahigh degree however the intermediate stages of the polymer condensation, reaction liquids of varying viscosity depending on the molecular weight are obtained.

Intheabovespecificexampleanyofthehereinabcve listed bi-, trior other multifunctional mercapto may be substituted. There is preferably used a minimum number of acid groups, e. g.. carbox'yl groups, equal to the number of 8H groups.

[sample 2 ProceedasinExa-mpleisubstituting2mols of 1,2,3 trimercapto propane for the 1 mol of dimercaptoethaneandtmolsofmaleicacid (or anhydride) for the 1 mol of maleic acid. I

Mixtures containing poiymercapto compounds having difierent specific structure or different desrees of functionality in respect of mercapto groups and mixtures of polymercapto compounds and polyhydric alcohols may be reacted with We acids to produce interesting and valuable copoiymers. Here again, the preferred minimum proportion of polybasic acid is that necesmrytoprovideatotalnumberofacidsroups. e. g.. carboxyl groups at least equal to the total number of mercapto or mercapto plus hydroxyl sroupssothattheremaybeenoughtotalacid functional groups to balance the thioaicohol functions or thioalcohol plus alcohol functions. 'lhereactantshavingafunctionalityoi'threeor more produce cross-linkage whereas when all the reactants have a functionality limited to two. linear polymers are obtained. By varying the moportion of components producing linear growth to those producing cross-linkage, in the production of copolymers, the extent of cross-linkage myhecontrolled.

'lheproducticnofcopolymerswilibeiliustratedinthefollowingexamples.

Paxnaarrol or Coronnsxas lmmple 3 amplei.

Imp! 4 Proceed as in Example 1 substituting a mixture of 2 mols of 1. '2, 3 trimercapto n-propane and 1 mol of pent'aerythritol for the 1 mol of dimerethan'e used'in Example 1 and 5 mols of phthalic acid orphthalic anhydride forthe lmol dusedinExampi 1.

sample 5 Proeeedasinlxamplelsubstitutingamixture Imolsof1,2,3trimercapton-propane. lmol ofdimercapto ethaneandimol of pentaerythrltoli'ortbeImoioi'dimercaptoethaneusedin Example 1 and 6 mols of fumaric acid for the lmolofmaleicacidusedinExamplel.

Example 6 ProceedasinExamplelsubstitutingamixture of 2 mols of 1,5 dimercapto 3 mercaptomethyl pentane, 1 mol of dimercapto ethane and 1 moi of ethylene glycol for the 1 mol of dimercapto ethane of Example 1 and 5 mols of maleic acid or anhydride for the 1 moi of maieic acid used in Example 1.

Example 7 ProceedasinExamplelsubstitut-inalmolof 1, 2. 3 trimercapto n-propane and 1 mol 01 dimercapto ethane for the 1 mol of dimercapto ethane of Example 1 and 2.5 mols of maleic acid for the 1 mol of maleic acid of Example 1.

Example 8 ProceedasinExamplelsubstitutingamixture of 1 mol of 1. 2. 3 trimercapto n-propane and 1 mol of pentaerythritol for the 1 mol of dimercaptoethane of Example 1 and 3.5 mols of adipic acid for the 1 mol of maieic acid of Example 1.

Example 10 Proceedasinlsubstitutingamixture I of 1 mol of dimercaptoethane and 1 moi at B8 dihydroxydiethyl disulfide (see Table II) for the 1mo1ofdimercaptoethaneofExampie1and2 molsofadipicacidforthelmolofmaleicacidof Example 1.

Example 11 Proceed as in Example 10 substituting for the glycolthereinused. 1molofpentaerythritoland uaing3molsofphthalicacidinsteadofthel mols of adipic acid.

Inthe above examples, polymercapto compounds in general may be substituted to:- those specifically usedinsaidexamplesandpolyhydricalcoholsin general may be substituted for those specifically used in said examples. Moreover. P lybasic acids in general may be substituted for those specifically used in said examples.

By employing a mixture of a monobasic acid with polybasic acids. the character of the producia may be modified. Various monobasic acids. particularly fatty acids both lower and higher may be used, as for example, acetic, propionic, butyric. valeric. palmitic, iauric, stearic. etc.

Such procedure may be exemplified by substituting in any of the above examples a portion of the polybasic acid by monobasic acid, the proportion of moncbasic acid substituted may vary overawiderange.asiorexampie,rrom5to50 molar per cent of the monobasic acid in relation to the polybasic acid. A specific example of this procedure will be illustrated as iollows:

Example 12 Proceed as in Example 5. substituting 5 mois of fumaric acid and 2 mols of iauric acid for the 6 mols of fumaric acid in Example 5.

In the reactions above set forth the catalyst may be omitted but is preferably used to increase the velocity of the reaction. The preferred catalysts are mineral or strong acids or acid salts, e. g., hydrochloric, sulfuric, phosphoric, chlorsuifonic, trichloracetic, etc., and acid salts or esters. Salts and compounds splitting off acid. e. g., by hydrolysismay also be used, e. g., AlCla, SOzClz, S2Clz, etc.

The invention is not limited to the reaction of polybasic acids with monomeric polymercapto compounds since the reaction is one of general application to polymercapto compounds in the polymeric as well as in the monomeric condition. By employing the splitting or cleavage technique disclosed in our copending applications Ser. No. 502,298, filed September 14, 1943, and Ser. No. 512,594, filed December 2, 1943, both of which are now abandoned it is possible to prepare a wide variety of sulfide polymers in liquid form and the present invention may be applied advantageously to such polymeric products by the reaction of polybasic acids therewith. It has been found that a molecular weight of about 16,000 is an approximate upper limit consistent with fluidity.

Examples of the application of the invention to polymeric polymercapto compounds having varying degrees of molecular weight will be described. When the term molecular weight is applied to polymeric polymercapto compounds, it does not necessarily mean the molecular weight of a single chemical entity because in many'cases the polymer will consist of a mixture of a large number of specifically difierent individual polymercapto compounds, as for example, when a polysulfide polymer is subjected to the said cleavage or splitting technique. However, the polymers thus obtained will havearr average molecular weight.

There will first be described the production of polysulfide polymers having varying degrees of average molecular size followed by a description of the reaction thereof with polybasic acids.

Example 13 6 liters of 2-molar sodium disulflde solution are placed in a suitable flask equipped with means for mechanical agitation and a reflux condenser and to the polysulflde solution are added 50 grams of crystalline magnesium chloride and 20 grams of sodium hydroxide thereby leading to a gelatinous dispersion of magnesium hydroxide in the polysulfide solution. The agitator is kept running while the polysulfide is heated to a temperature of about 70 C. and 10 mols of BB dichloro diethyl formal are added slowly to the polysulflde mixture at a ratesuch that about one hour is required for the complete addition of the organic dihalide. The temperature during this addition should be controlled in such manner that it does not go above about 100 to 105 C. in order to prevent refluxing.

The stirred mixture is held at a temperature of about 105 C. for about an hour after all the organic dihalide is into the reaction after which the agitator is stopped and the latex like dispersion of the polymer is permitted to settle out from the liquid. After settling of the polymer is fairly complete the supernatant liquid is withdrawn by any suitable means as by siphoning and the dispersion is freed from soluble salts by repeated washing with warm water. This is most easily done by stirring the latex'through the wash water and allowing it to settle, then withdrawing the water and replacing it with fresh.

To produce a satisfactorily high molecular weight it is desirable to treat the washed latex 500. While the accuse with about 2% liters of a 2-molar solution of a sodium disulflde similar to the one used in the preparation of the polymer. The suspension is then heated with this fresh charge of disulfide for about one hour at "100-405 0., afterwhich the polysulfide is washed out using thesame technique as that described above for the initial washing of the latex. The latex like dispersion of the polymer resulting from the foregoing steps is, when coagulated, a tough, rubbery polymeric substance, the molecular weight of which is very high, certainly well over 50,000 and rough indications show it to have a molecular weight of approximately 100,000 to 120,000 and in some cases even higher.

It has been found that this high molecular weight polymer can be reduced to a dimercapto polymer having a molecular weight of approximately 16,000, which is about the upper limit consistent with fluidity, by proceeding in the followin manner.

To the washed latex produced as above described is added 0.09 gram of sodium hydrosulfide and 5 grams of sodium sulfite. The volume of the fluid dispersion is heated with constant agitation to a temperature of about C. for 30 minutes. The agitator is stopped and the dispersed polymer is permitted to settle out as described above and is then washed free from soluble salts in the manneralready described.

When this split polymer is coagulated, as for example by making slightly acid with acetic acid, and the coagulum dried by anysuitable means the product is found to be a very stiff viscous liquid which is capable of flowing under its own weight if given suilicient time to do so. It is found by chemical test to consist principally of a polymer having chain molecules terminated by mercaptan or thiol groups. Determinations of molecular weight both cryoscopically and by end group titration show its molecular weight to be an average of about 16,000 although as in the case of nearly all synthetic polymers, this figme is found to be an average or statistical one since it can be demonstrated that fractions can be separated having somewhat higher as well as fractions having somewhat lower molecular weights than the mean.

Example 14 Proceed exactly as in Example 13 to produce the high polymer but in the second part of the example involving the treatment with sodium hydrosulflde and sulflte the'proportions of the splitting agents are varied in such a manner that 3.5 grams of sodium hydrosulfide and 15 grams of sodium sulflte are used. The volume is adjusted as described in Example 11 and the same heating technique is used. The coagulated and dried polymer from this example is found to be a slightly viscous liquid having a viscosity corresponding to that of a very thin syrup and viscosity measurements indicate that it has an absolute viscosity of 5 to 10 centipoises. Molecular weight determinations on this product indicate the molecule to be about 3 units long and the number molecular weight shows an average of about 500.

The above Examples 13 and 14 describe the production of polymers having an upper limit of average molecular weight of about 16,000 and a lower limit of average molecular weight of about present invention, involving as it does the reaction of polybasic acids with polymercapto compounds generally, is not of course limitedtotheuse inthisreaction-oipolymers having an average molecular size indicated by the limits 0! 500 to 18,000 for the average molecular weights nevertheless this ranae as far as the polymers themselves are concerned, i. e.. not necessarily dependent upon their reaction with polybasicacidaisacriticalranaeiormanypub poses. Itthemolecularsiseistoolargethe fluidityotthematerialiadeereasedtoapointwhere it u not practical to use it for purposes where fluidity is necessary. the character of the material then becoming more that of a rubber-like solid rather than a iiowable liquid whereas it the molecularweightistoolowthecharacterotthe material then becomes that of a somewhat volatileverythlnliquidwhiehissoreadllyabaorbed hyanykindotporousmaterialwithwhichit comes into contact that its application becomes diilcidtiorthepurposesoiaeealant.

To obtain polymers having average molecular sizes intermediate between the lower limit of 500 and the upper limit of 16,000, the proportions of hydrosulflde and sullite are varied as indicated in Examples 13 and i4.

Having shown details of the production of certain preferred polymeric polymercapto compounds in Examples 13 and 14, there will now be described specific illustrative instances 0! the reaction thereoi with polybasic acids.

Example 15 Proceed as in Example 1 substituting for the 1 moi of dimercapto ethane in that example 500 grams oi the fluid polymer obtained according to Example 14. The product is a rubber-like polymer. and thus sharply distinguished in propertia from the vwax-like polymer obtained by the reaction between malcic acid and dimercaptn ethane in Example 1.

Iumple 16 ProceedasinExamplelusinginsteadoidimercaplo ethane the polymer obtained as in Example 14 having an average molecular weight of about 16,000 and reacting this with slightly more than an equimolecular weight oi maleic acid or anhydrlde. The product obtained is a rubberlike polymer, and the action of the acid on the polymer having the molecular weight of about 16,000 is a species of curing eiiect.

What is claimed is:

Process which comprises heating dimercapto ethane and maleic acid in equimolecular proportions in the presence of a mineral acid catalyst, splitting oil water between the reactants and ohtaining a polyester product.

JOSEPH C. PATRICK. HARRY R. FERGUSON.

REFERENCES CITED Theiollowingreterencesareotrecordinthe tile oithis patent:

UNI'I'EDSTATIS PATENTS Number Name Date 1,984,417 Mark et al. Dec. 8. 1934 2,149,857 Mikeska et al Mar. '1, 1939 2,195,380 Patrick Mar. 28. 1940 2,843,808 Bchlack Mar. 7. 1944 

